We reasoned that the experience with two languages and the increased need for cognitive control to use them appropriately would result in brain changes in Spanish-English bilinguals when compared with English-speaking monolinguals.

And in fact greater gray matter for bilinguals was observed in frontal and parietal brain regions that are involved in executive control.”

Speaking both the languages is key to the differences, though.

The researchers also looked at people who were bilingual in English as well as sign-language — which is obviously not spoken.

Dr Olumide Olulade, the study’s lead author, said:

“Unlike the findings for the Spanish-English bilinguals, we found no evidence for greater gray matter in the ASL-English bilinguals.

Thus we conclude that the management of two spoken languages in the same modality, rather than simply a larger vocabulary, leads to the differences we observed in the Spanish-English bilinguals.”